Field of the Invention
The present invention relates to an electronic apparatus with a fan motor.
Description of the Related Art
A numerical controller used for the control of a machine tool or the like generates heat during use and may sometimes malfunction. To prevent this, in general, the housing of an electronic apparatus that comprises the numerical controller is provided with vent holes, and a fan motor is mounted in the vicinity of these vent holes such that it ventilates the interior of the housing to cool the numerical controller.
In some cases, the operation of the fan motor may fluctuate due to service life expiration of a built-in bearing, clogging by contamination, etc. If the fan motor thus varied in operation continues to be operated, it sometimes cannot perform appropriate cooling. If the operation of the motor is further continued, it may possibly hinder the operation of the numerical controller.
To overcome this, the service life of the fan motor is detected in advance. Characteristic fluctuations occur due to increase in mechanical rotational load caused by bearing wear during prolonged operation, clogging by contamination, etc. Thus, the life expectancy of the fan motor is detected by detecting these characteristic fluctuations.
Japanese Patent Application Laid-Open No. 2010-136609 discloses a technique to determine whether or not the cooling capacity of an inverter device is reduced, based on the result of comparison between the value of a thermal time constant calculated by a thermal time constant calculating circuit and a reference value of the thermal time constant stored beforehand in a memory, in order to measure a reduction in the cooling capacity due to service life expiration of a cooling fan, clogging, etc.
Japanese Patent Application Laid-Open No. 2007-139202 discloses a technique in which a controller for a water heater detects an abnormality of a component of the water heater, stops the operation of the component of which abnormality is detected and restarts the operation of the component, and determines that the component is out of order if the number of restarts of the operation of the component reaches a predetermined value.
Japanese Patent Application Laid-Open No. 2002-101570 discloses a technique in which a power supply section or uninterruptible power supply unit of an electronic apparatus is provided with a detection function to determine the life expectancy and operation state of a fan motor and notify the main body of the electronic apparatus of the determined conditions.
Japanese Patent Application Laid-Open No. 2001-298989 discloses a technique to determine whether or not the end of the service life of a DC fan motor of a vending machine is approached, based on the relationship between the actual speed of the DC fan motor and a reference rotational speed.
In the techniques disclosed in the four patent documents described above, the determination is made based on the result of comparison of the thermal time constant, fan speed, commercial power supply input, and DC fan motor speed with reference values. However, these techniques are characterized in that characteristic fluctuations during operation are detected.
FIG. 6 is a flowchart showing a flow of processing for the determination of the state of a prior art fan motor. The following is a sequential description of steps of the processing shown in this flowchart.
(Step SA1) The electronic apparatus is powered on.
(Step SA2) The fan motor is rotated.
(Step SA3) The state of the fan motor in rotation is determined. If the fan motor is rotating normally, the processing proceeds to Step SA4. If the motor is not rotating, that is, if it is defective, the processing proceeds to Step SA5. If the motor is rotating at a low speed, that is, if its performance is deteriorated, the processing proceeds to Step SA6.
(Step SA4) The operation of the electronic apparatus is continued and the processing returns to Step SA3.
(Step SA5) The fan motor is determined to be defective and the operation of the electronic apparatus is stopped.
(Step SA6) While the operation of the electronic apparatus is continued, an indication to prompt replacement of the fan motor is displayed due to the occurrence of deterioration.
(Step SA7) The state of the fan motor is determined. A criterion for this determination may be the same as or different from that for the determination in Step SA3. If the fan motor is rotating normally or at a low speed (that is, if the motor performance is deteriorated), the processing proceeds to Step SA6. If the motor is not rotating (that is, if the motor is defective), the processing proceeds to Step SA8.
(Step SA8) The fan motor is determined to be defective and the operation of the electronic apparatus is stopped.
The fan motor may be operated continuously or intermittently (repeating operation and stop). Such intermittent operation involves a stop period. If the operation is restarted after a stop, therefore, the coefficient of friction becomes higher than in continuous operation, the viscosity of bearing grease is increased by a temperature reduction due to the stop of operation, or contaminants are solidified. In some cases, therefore, the mechanical rotational load may become higher than in continuous operation. Thus, start failure may occur before characteristic fluctuations are detected.